A056275 Number of primitive (aperiodic) word structures of length n using a 4-ary alphabet.

1, 1, 4, 13, 50, 181, 714, 2780, 11046, 43895, 175274, 699875, 2798250, 11188191, 44747380, 178970560, 715860650, 2863365834, 11453377194, 45813202675, 183252461532, 733008625151, 2932033104554, 11728127521060, 46912504507000, 187649998452735, 750599971438464

Offset: 1

Author

Marks R. Nester

Keywords

• nonn

Comments

Permuting the alphabet will not change a word structure. Thus aabc and bbca have the same structure.

References

• M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]

Crossrefs

Cf. A008683, A054719.

Formula

a(n) = Sum_{d|n} mu(d)*A007581(n/d-1).